The first home in a permanent community, outside a tree or a cave, was constructed about 11,000 years ago. Although these homes were made of reeds and mud, they had a stone base. About 1000 years later, in the town of Jericho, homes were built by using bricks made from baked mud. Wall and roof construction had improved, but foundations still were made from stone. Later the Egyptians and the Romans used cementing materials to mortar joints. However, the use of portland cement, the kind that is used to make modern concrete, wasn't developed until 1824.

With concrete, the process of building a foundation has become relatively simple. No more stacking and cementing heavy stones. Once mixed, the pasty gray substance is poured directly into an earthen trench or wooden (or paper) forms. Imbedded steel bars are used to improve strength, and a myriad of steel gadgets are strategically placed into the wet concrete to help with the attachment of wood and other building materials.

Not every structure needs a foundation. A lightweight storage shed can be placed on a four-inch thick concrete slab _ without a foundation. However, when it comes to a room addition or a wood deck, building a sturdy foundation is a must.

Before concrete is poured, it must be mixed. You can purchase it from a ready-mix plant or mix it yourself. Mixing is hard work and should be reserved for smaller projects like walks and small patios. It is as simple as 1-2-3. By volume, use 1 part portland cement, 2 1/4 parts sand (don't use sea sand - salt destroys concrete), and 3 parts rock (3/4-inch to 1 1/2-inch rock is OK).

As we mentioned, forms are used to create the desired shape of the concrete. They hold the wet concrete in place until it dries in the same sort of way that a cake pan holds and shapes batter. The concrete is poured into the forms which remain in place until after it dries. Then the forms are removed. With an addition, money can be saved by using framing materials for the forms. After the forms have been stripped away from the foundation they can be cleaned and recycled. Being used as form material has no negative impact on framing lumber. Spray form oil onto the forms before they are used to make them easier to remove from the dried concrete.

Steel reinforcing bars improve the strength of concrete. They usually are placed horizontally within the foundation wall and run continuously throughout the entire structure. A foundation that costs $2,000 might have only about $100 worth of steel in it - a lot of added strength for little money. Most residential foundations contain only two or three bars of reinforcing steel. By adding an extra bar or two, you can substantially increase your foundation's strength without adding a great deal of cost.

Anchor bolts (the more the better) are imbedded into the top surface of the foundation wall to securely bolt the wood framing to the foundation.

A foundation has two basic design components - the footing and the wall. The footing makes up the base and is located underground. The footing size and depth is engineered to carry and evenly distribute the weight of the house onto the earth. Sometimes the footing is a continuous concrete beam that is wider than it is tall, and sometimes it is a square or rectangular pad. In other instances the footing is cylindrical. Here, a hole is dug straight down into the ground. A deep round footing is known as a "pier footing" or "pier." In all cases, the footing is built to rest below the frost line which is the deepest point at which the earth freezes in the winter.

Note: It is extremely important that the foundation wall be at least eight-inches above the ground. At this distance it can be used to safely separate the wooden parts of the structure from the earth. The wall protects the wooden parts from water damage and reduces the chance of a termite attack. Whenever earth and wood are in contact with each other, termites can travel into a wood structure unnoticed. With a concrete wall separating earth and wood, termites must tunnel up the concrete wall to get to the wood. These tunnels make the termites easy to discover.

Most folks believe that you have to strengthen the walls to carry the extra load when adding a second story to a home. Actually, you don't. A wall built with 2x4 studs spaced 16 inches apart easily will carry a second floor without modification. It is the foundation that usually won't tolerate the extra weight.

Finally, when adding on, the new foundation should exactly match the size and shape of your existing one. Both the new foundation and the old one need to react to ground movement in the same way. Can you imagine your addition remaining solidly at one level while the old portion of the home rises or falls an inch or more? Using the same size and shape foundation doesn't mean that you have to sacrifice strength. Use the same shape and size, but include stronger concrete, more steel, more anchor bolts and modern hold-downs.